Heatmiser NeoStat v2 Starting Ecodan Every 10-15 minutes

Hi guys,

I typically have my Ecodan units in the off state unless they are actively heating, recently I removed Glycol from my system and with the cold spell over the past few days I have invoked ‘Cold Weather Protection’ mode which has them switched on when the temperature is <5 degrees C (so the Ecodan internal anti-freeze system can function).

I happened to notice that one of my systems was firing up in ‘heat zones’ mode every 10-15 minutes and running for 5 minutes before returning to idle state. Effectively cycling the heat pump and chewing through electricity. This was happening at a time when all of the room thermostats (Heatmiser NeoStat v2) were in standby mode.

I believe this behaviour was being caused by the ‘Optimum Start’ feature of the NeoStat thermostats which was previously enabled on each individual thermostat (set to 3hrs by default I believe). I’ve disabled this setting on each thermostat and the cycling has stopped for the past four hours.

I tried searching for this but didn’t find anything quite like it so thought it worth documenting here, in the hope that it saves someone from the frustrating waste of time that I’ve suffered tracking this down today!

This scenario is eluded to in Heatmisers FAQ;

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Looks like I spoke too soon, the heat pump is still cycling every 10-15mins running for 5 mins and then going back to standby.

I’m scratching my head, would love to hear if anyone else has any ideas…

I have two Ecodan’s both set to wc curve, both have external thermostats connected to IN1, dip switch 2-1 is set to ON for both systems (zone1 operation stop at thermostat open).

I’ve checked every setting on the units and with the exception of those relating to DHW/Immersion (only the troublesome unit has DHW) they are configured identically.

The Ecodan running upstairs radiators doesn’t exhibit this behaviour, it has a tado external thermostat.

The Ecodan running downstairs UFH and DHW which is having the issue has a pair of Heatmiser UH8 manifolds with NeoStat v2 thermostats attached to each.

I tried powering off the UH8 manifolds/thermostats this morning so they couldn’t call for heat, the behaviour persists with these powered off.

Hello @Dan_Nichols Im sure I noticed this as well with the heatmiser neoAir, there is the failsafe mode that runs for 12 mins every hour if the neoAir is not detected, but that’s a different time period from what your seeing.

In the end we removed the heatmiser controls on that system and ran all the underfloor zones fully open and used the Ecodan’s own controller as the room thermostat instead (moving it from the garage to the kitchen/diner). Results seemed to be much better.

More recently on another system a Grant heat pump with a Honeywell Home T3 thermostat did display this exact issue and in that thermostat’s case there was a maximum number of starts per hour and minimum run time setting that could be adjusted. In that cause we reduced the number of starts to 3 starts per hour and minimum 5 mins runtime (unfortunatly the maximum setting).

It was doing this:

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Thanks @TrystanLea. My UH8’s have wired room thermostats so no chance of them not reporting in, although they are in standby mode (that’s how I stop them individually calling for heat if the average temperature is within an acceptable range).

I have disconnected one of the two UH8’s again this afternoon and so far the system is behaving. I’m not going to declare victory just yet though as I thought the same yesterday evening.

I don’t have a Mitsubishi wireless room controller at the moment and that would take away my ability to control the call for heat in the way I am doing at the moment. If all else fails I’ll knock up an ESP32 with a relay or similar to control the call for heat.

The image below shows the heat pump switching to ‘Heat Zones’ periodically throughout the day whilst ‘Heating Downstairs’ is Off (this coincides with all thermostats being in standby mode). The only way to stop it was to shutdown the heat pump (HVAC mode = Off).

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So the phantom calls for heat continue (sometimes with a few hours gap lulling me into a false sense of victory).

I’m going to lose the call for heat from the UH8’s and add a relay to my ESP32 which will be monitoring flow temperatures through the LLH.

Now the heatmiser thermostats are literally just a very fancy wired room temperature sensor…might have to replace them with something that can do this plus be useful for home automation!

Hi, I may be suffering from the same effect you describe. Some background first. My 5kW ecodan heats a new build small mid terrace house with a pre packaged cylinder in the roof. There is UFH up and down stairs on two separate UH8 controllers feeding IN1 and IN6 terminals on the control panel. Each room had a separate thermostat giving 8 in all. Total overkill, probably building regs, and costing a fortune in batteries. Anyway, replaced the lot with a Tado in the hallway to give a perfectly adequate control system. Other improvement was to calibrate the flow and return thermistors, they were reading about 5’C low and so real flow temperature was too high.
In summary, IN1 and IN6 are connected to volt free relays in the Tado. When the thermostats are satisfied, the associated pumps stop on each zone. However the heat pump remains in a standby state where the water pump to the heat pump remains on and the heat pump fires up occasionally to keep the water in the loop hot. I have looked everywhere to find out if these external thermostats can close down the heat pump as well as the local heating circuit. Does this sound like what you are experiencing or better still, found a solution?

Hi Steve, my issue was caused by the Heatmiser stats/manifold calling for heat when there was no demand. Did I understand correctly that you no longer have the Heatmiser connected to the call for heat as you’ve replaced with the Tado?

If so then I happen to have a second Ecodan system with Tado connected to call for heat and this system does not have the random unprompted call for heat issue.

Do you have freeze stat enabled on your system? If so it could be that which is running your system to avoid the external pipes freezing (mine runs from around 6C I believe). If you have glycol in the system you can turn freeze stat off.

Hi Dan, Yes, I have replaced the Heatmiser system with a Tado. The Heatmiser and actuators were taking about 50W plus batteries at £25 a year. A single thermostat in the hall worked perfectly for me. In fact, the upstairs heating is never used as enough heat leaked to the bedrooms from down stairs for comfort. With the UFH taking several hours to respond, the Heatmiser was a waste of space trying to cope with a real household where doors open and close, solar gain, cooking etc which can happen in much shorter times.
The conversion was simple, unscrew all the actuators so that all the heating circuits are open and swap the ecodan control leads from the Heatmiser relay to the Tado.
The Tado turns off the pump to the heating circuit but the heat pump and its circulating pump are still active. A bit like leaving a car in neutral with the engine running. The ecodan is taking about 250W (real Watts from the Smart Meter) in this standby mode.
I can manually turn off the heat pump from the control panel but I want this to happen when the thermostats are satisfied. The frost protection is turned off so this doesn’t explain the problem.
I’m trying to find out if this is a setup problem, normal operation or something is faulty. I’ve tried the classic turn it off and on again but this did not work…

That is unusual. I’d expect the heat pump to stop running when there’s no call for heat. What does MelCloud’s “Operation Mode” report look like?

Double-check the inputs and DIP switches.
Does it think it has a buffer? Or two zones?

Hi Tim, Thanks for your comments. The operation mode report is not very informative. ‘Power off’ when I have manually turned the system off at the control panel, ‘Heating’ when the compressor is on and ‘Stop’ when the compressor is off but the primary pump still running.
I’ve assumed the installer knew what he was doing and have not messed with the DIP switches so far ( ok, I’m naive!) According to the manual SW2-7 should be on for 2 zone control, it is off in this system. This is the obvious thing to try but I won’t have an opportunity to crawl into the roof space for a couple of weeks.
The thermostat connections look ok, about 12V with the relay open and 0V on closure. I might try opening and shorting the connectors on the PCB with no long wires to see if any electrical noise is being picked up, another visit into the roof space :rage: